Value returning 1.#INF000

Question

An intersection algorithm isn't working; one of the values, tmin, evaluates to 1.#INF000 - what does this mean and why is it occurring? tmax seems to be fine.

float Ray::Intersects(BoundingBox boundingBox)
{
// direction is unit direction vector of the ray
D3DXVECTOR3 dirfrac(
    1.0f / direction.x,
    1.0f / direction.y,
    1.0f / direction.z);

D3DXVECTOR3 min = boundingBox.Min();
D3DXVECTOR3 max = boundingBox.Max();

//min and max are the negative and positive corners of the bounding box
float t1 = (min.x - origin.x) * dirfrac.x;
float t2 = (max.x - origin.x) * dirfrac.x;
float t3 = (min.y - origin.y) * dirfrac.y;
float t4 = (max.y - origin.y) * dirfrac.y;
float t5 = (min.z - origin.z) * dirfrac.z;
float t6 = (max.z - origin.z) * dirfrac.z;

float tmin = max(max(min(t1, t2), min(t3, t4)), min(t5, t6));
float tmax = min(min(max(t1, t2), max(t3, t4)), max(t5, t6));

// if tmax < 0, ray (line) is intersecting AABB, but whole AABB is behind us
if (tmax < 0) { return -1; }

// if tmin > tmax, ray doesn't intersect AABB
if (tmin > tmax) { return -1; } //HERE TMIN IS 1.#INFOOO

return tmin; //THIS IS NEVER REACHED
}

Answer 1

1.#INF000 is most likely the positive infinity. If you are getting this, it means one of the following in case of your code:

• t1 and t2 are both infinite
• t3 and t4 are both infinite
• t5 and t6 are both infinite

My guess is that you are probably dividing by zero somewhere, most likely when you calculate the value of dirfrac.